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Adding 9, 19 and 99 Mental Maths Worksheet

Mental maths lesson 4: Add and take away 9, 19 and 99 · Set 532 · 40 questions
TalentJR

How to do it in your head (Round and adjust): Add 9, 19, 99: add 10, 20, 100, then take 1 away. Take away 9, 19, 99: take away 10, 20, 100, then add 1 back. Ask yourself: did I use too much or too little?

NameDateTime takenScore ___ / 40
  1. 1.16 + 9 =
  2. 2.26 + 19 =
  3. 3.31 − 19 =
  4. 4.451 − 99 =
  5. 5.60 − 29 =
  6. 6.57 − 9 =
  7. 7.55 − 9 =
  8. 8.50 − 29 =
  9. 9.71 + 29 =
  10. 10.137 + 99 =
  11. 11.56 − 19 =
  12. 12.261 − 99 =
  13. 13.88 − 9 =
  14. 14.71 − 19 =
  15. 15.665 + 99 =
  16. 16.535 + 99 =
  17. 17.57 + 19 =
  18. 18.90 − 19 =
  19. 19.63 + 29 =
  20. 20.59 − 19 =
  21. 21.412 + 99 =
  22. 22.28 + 29 =
  23. 23.60 + 29 =
  24. 24.43 − 9 =
  25. 25.303 − 99 =
  26. 26.52 − 9 =
  27. 27.288 + 99 =
  28. 28.88 − 29 =
  29. 29.498 + 99 =
  30. 30.55 + 9 =
  31. 31.750 + 99 =
  32. 32.58 + 19 =
  33. 33.46 − 9 =
  34. 34.38 + 9 =
  35. 35.63 − 9 =
  36. 36.714 − 99 =
  37. 37.93 − 19 =
  38. 38.39 + 19 =
  39. 39.76 − 9 =
  40. 40.374 − 99 =

Answer key

  1. 25
  2. 45
  3. 12
  4. 352
  5. 31
  6. 48
  7. 46
  8. 21
  9. 100
  10. 236
  11. 37
  12. 162
  13. 79
  14. 52
  15. 764
  16. 634
  17. 76
  18. 71
  19. 92
  20. 40
  21. 511
  22. 57
  23. 89
  24. 34
  25. 204
  26. 43
  27. 387
  28. 59
  29. 597
  30. 64
  31. 849
  32. 77
  33. 37
  34. 47
  35. 54
  36. 615
  37. 74
  38. 58
  39. 67
  40. 275

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